The present invention relates generally to a information signal copy managing method for managing copying of various information contents such as an audio signal and a video signal for example, an information signal output apparatus and an information signal recording apparatus that operate on the basis of this method, and a recording medium for recording information signals.
Recent widespread proliferation of digital content provided by the Internet, a compact disc (CD), and a digital video disc (DVD) for example poses a new problem of the copyright infringement by the unauthorized copy (duplication) of digital content. To prevent the unauthorized copy, a method has been proposed in which additional information for copy control is attached to digital content.
The prevention of copying is controlled in two manners according to information sources; no copy is allowed at all and copy is allowed only once and therefore a copy cannot be further duplicated (copy control with limited copy generation). The former is applied the original software which is created and sold by content makers as with DVD-ROMs for example. The latter is applied to the information which is broadcast in broadcast media for example.
The copy control with limited copy generation requires schemes for effectively controlling copy generation. The schemes include SCMS (Serial Copy Management System) and CGMS (Copy Generation Management System) for example.
In SCMS, digital copy is permitted only once by use of a copy enable/disable flag and a category code indicative of a digital audio system type such as CD (Compact Disc) or DAT (Digital Audio Tape) for example, these flag and category code being transmitted with a digital audio signal.
Namely, SCMS information consisting of the copy enable/disable flag and the category code to be transmitted with a digital audio signal allows copy of the digital audio signal of the first generation but does now allow copying of the duplicated digital audio signal.
In CGMS, in the case of an analog image signal for example, 2-bit additional information for copy control is superimposed on a particular horizontal interval in the signal""s vertical blanking period and, in the case of a digital image signal, this additional information is added to digital image data for transmission.
The 2-bit additional information (hereafter referred to as CGMS information) conveys the following means:
xe2x80x9c00xe2x80x9d . . . copy permitted;
xe2x80x9c10xe2x80x9d . . . copy permitted only once (only for one generation); and
xe2x80x9c11xe2x80x9d . . . copy prohibited.
If the CGMS information attached to image information is xe2x80x9c10xe2x80x9d, a CGMS-compliant recording apparatus determines that the image information can be duplicated and executes a recording (or duplicating) operation. As a result, CGMS information xe2x80x9c11xe2x80x9d is added to the recorded image information. When the CGMS information thus attached to image information to be recorded is xe2x80x9c11xe2x80x9d, the CGMS-compliant apparatus determines that this image signal cannot be copied, disabling further recording processing.
Thus, SCMS and CGMS control the copy generation of audio signals and video signals (or image information).
Use of above-mentioned SCMS or CGMS can prevent a copied information signal from being copied onto another recording medium. However, there is still a problem that a first-generation information signal provided by a content maker in the form of a CD for example can be infinitely duplicated from that CD by use of the same recording apparatus.
Consequently, instead of the above-mentioned copy generation control schemes which pose a danger of unauthorized mass copy, a scheme may be proposed in which information signals are provided in the form of copy-prohibited discs for example, thereby disabling copying of information signals from the beginning.
This scheme can securely protect the copyright of information signals. However, this scheme allows users to use information signals only from the copy-inhibited disc, thereby significantly limiting user advantages in the use of information signals.
For example, the copy-prohibited disc limits the usage of information signals in which the user selects desired titles of music from the disc and duplicates the selected titles onto a small-sized magneto-optical disc called an MD (Mini Disc) or a cassette tape for reproduction on a car stereo device or a portable player for personal enjoyment.
To overcome this problem, a method has been proposed in which the copyright of information signals can be properly protected and, at the same time, user convenience for using information signals by duplicating them within a limited range can be ensured. To be specific, this method limits the number of times copy can be made in which each recording apparatus controls the number times copy is made for each piece of information content (xe2x80x9cinformation contentxe2x80x9d herein denotes each music or movie title for example), one title being copied only by the predetermined number of times.
However, if this proposed method decrements the number of times copy can be made when the stop key of a recording apparatus is inadvertently pressed during recording of a title for example, it counts up for an incomplete copy, putting the user at a great disadvantage.
It is therefore an object of the present invention to provide an information signal copy managing apparatus, an information signal recording apparatus, an information signal output apparatus, and a recording medium that overcome the above-mentioned problems by allowing the user to fully understand the completion of copy and recording of each piece of information content.
In carrying out the invention and according to one aspect thereof, there is provided an information signal copy managing method comprising the steps of: superimposing information indicative of a start of and information indicative of an end of a portion of each piece of information content, the portion being covered by copyright, onto each piece of information content as electronic watermark information to transmit a resultant information signal; and, when copying and recording the information signal, determining completion of copying of each piece of information content when both of the information indicative of the start of and the information indicative of the end of that portion are detected from the electronic watermark information, thereby executing copy management.
Detection of the information indicative of the start of and the information indicative of the end of the copyrighted portion as electronic watermark information is determined as the completion of copying of the information content. Consequently, a copy operation that failed due to an erroneous user operation for example is not recognized as complete, thereby guaranteeing user advantages in copying information signals within a limited range.
In addition, start position information and end position information are superimposed on the information content as electronic watermark information. This makes it difficult to tamper the start and end position information, thereby properly protecting the copyright of the provided information content.